There is considerable variation in the intensity of the green suffusion, but the best exhibition birds of the 1930s showed very little and also had very faint wing markings.
Budgerigars were first introduced into Europe by the ornithologist and bird artist, John Gould, in 1840,[1][2] when he imported to England a pair which had been bred by his brother-in-law, Charles Coxon.
For the first thirty years of their domestication only the wild-type Light Green budgerigar was known, but in 1872[4] birds with greenish-yellow bodies and very pale wing markings were reported from Belgium (in both Brussels and Antwerp) and Germany (in both Kassel and Berlin).
In 1896, George Keartland of the Calvert Expedition to the Great Sandy Desert of Western Australia, observed a yellow budgerigar flying wild in a flock on three occasions.
That is, the presence of a single wild-type allele is sufficient to permit the production of the normal number of melanin granules.
[6] In a bird which has two Dilute alleles (the homozygote) the number of melanin granules is greatly reduced, to around 5% of the normal amount.
This results in a much reduced intensity of the black markings, and less absorption of light which passes through the cloudy layer in the medulla of barbs.